The centre-back's previous deal at the Etihad Stadium had been due to expire in the summer of 2018.
However, having agreed to an extension, the 28-year-old has committed himself to the champions until 2019.
"When I arrived in 2008, I could never have dreamed that we could achieve what we have over the last six years but, for me, this is just the start of the journey," he told the club's official website.
"This team is stronger now than it's ever been. We have competition for places in every position and a dressing room full of exceptional, motivated people who want to continue making history together.
"Lifting two Premier League titles, the FA Cup and the Capital One Cup have been four of the best days of my life but I believe that there are many more of these occasions ahead."